U.S. patent application number 10/955174 was filed with the patent office on 2006-03-30 for unified multi-part head for a staked fastener.
Invention is credited to Clark A. Denslow.
Application Number | 20060067806 10/955174 |
Document ID | / |
Family ID | 36099321 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060067806 |
Kind Code |
A1 |
Denslow; Clark A. |
March 30, 2006 |
Unified multi-part head for a staked fastener
Abstract
A unified multi-part head for a staked fastener wherein the
unified multi-part head is made from a first member in combination
with a supplemental member, and the two members have at least one
shared fiber. In a staking operation that forms the unified
multi-part head, the operation is conducted in such a manner that a
portion of a fiber, initially within the first member or the
supplemental member, crosses the boundary therebetween creating the
shared fiber, i.e., a segment of a single fiber is embedded in the
first member and a segment is embedded in the supplemental
member.
Inventors: |
Denslow; Clark A.; (Madison,
CT) |
Correspondence
Address: |
William B. Gowanlock
16 Town Crier Lane
Madison
CT
06643
US
|
Family ID: |
36099321 |
Appl. No.: |
10/955174 |
Filed: |
September 30, 2004 |
Current U.S.
Class: |
411/504 |
Current CPC
Class: |
B29C 66/81423 20130101;
B29C 66/71 20130101; F16B 19/06 20130101; Y10S 411/908 20130101;
Y10T 403/4966 20150115; B29C 66/81431 20130101; B29C 66/81429
20130101; Y10S 411/90 20130101; Y10T 29/49956 20150115; B29C
66/72141 20130101; B29K 2071/00 20130101; B29K 2309/08 20130101;
Y10T 29/49966 20150115; Y10T 29/4997 20150115; B29K 2079/085
20130101; B29K 2307/04 20130101; B29C 66/71 20130101; B29C 66/8322
20130101; B29C 66/1122 20130101; B29C 66/7212 20130101; B29C
66/7212 20130101; B29C 65/36 20130101; B29C 66/43 20130101; B29C
66/21 20130101; F16B 19/1027 20130101; B29C 66/7212 20130101; B29C
65/601 20130101; Y10T 29/49915 20150115; B29C 66/71 20130101; F16B
5/04 20130101; Y10T 29/49801 20150115; Y10T 29/49943 20150115; B29C
66/3034 20130101; B29C 66/73921 20130101; Y10T 29/49957
20150115 |
Class at
Publication: |
411/504 |
International
Class: |
F16B 13/06 20060101
F16B013/06 |
Claims
1. A unified multi-part head for a staked fastener comprising: a
first member; a supplemental member, and a shared fiber embedded in
both the first member and the supplemental member creating a
combined first member and supplemental member.
2. The unified multi-part head of claim 1 wherein the supplemental
member has a key.
3. The unified multi-part head of claim 2 wherein the key has a
non-rotational cross-sectional shape.
4. The unified multi-part head of claim 1 wherein the supplemental
member is between the first member and a body.
5. The unified multi-part head of claim 1 wherein a majority of the
shared fiber is in the first member.
6. The unified multi-part head of claim 1 wherein the shared fiber
is created by a staking operation applied to the first member and
the supplemental member.
7. The unified multi-part head of claim 1 wherein the first member
contains thermoplastic and the supplemental member contains
thermoplastic.
8. The unified multi-part head of claim 1 further including a shank
extending from the combined first member and supplemental
member.
9. The unified multi-part head of claim 8 wherein the supplemental
member has at least one fiber.
10. A method of making a unified multi-part head for a staked
fastener comprising the steps of: providing a shank having a clinch
portion, the clinch portion having at least one fiber therein,
collocating a supplemental member proximate the clinch portion, and
staking the clinch portion to create a first member with the
supplemental member sufficiently to cause at least one of the at
least one fiber to become a shared fiber between the first member
and the supplemental member.
11. The method of claim 10 wherein in the step of collocating a
supplemental member, the supplemental member has a keyed
structure.
12. The method of claim 10 wherein in the step of collocating a
supplemental member, the supplemental member has a graduated
structure.
13. The method of claim 10 wherein in the step of staking, staking
employs an ultrasonic technique.
14. The method of claim 10 wherein in the step of staking, staking
employs an induction technique.
15. The method of claim 10 wherein in the step of providing a
shank, the shank has a grip member and fibers are located
therein.
16. The method of claim 15 wherein the fiber in the clinch portion
extends into the grip member.
17. The method of claim 10 having the additional step of providing
a substrate and wherein in the step of staking, the supplemental
member is between the substrate and the first member.
18. A method of making a rivet: providing a shank having an initial
head, passing the shank through a body, thereby defining on the
shank a gripping portion and a clinching portion having at least
one fiber therein, placing a supplemental member proximate the
clinching portion and the body, and staking the clinching portion
and the supplemental member creating a unified multi-part head.
19. The method of claim 18 wherein in the step of placing a
supplemental member proximate the clinching portion, the
supplemental member is placed such that in the step of staking the
at least a portion of the supplemental member will be trapped
between the first member and the body.
20. The method of claim 18 wherein in the step of providing a shank
having an initial head, the initial head has a first member and a
supplemental member with a fiber extending therebetween.
21. The method of claim 18 wherein in the step of staking, staking
employs an ultrasonic techniques.
22. The method of claim 18 wherein in the step of staking, staking
employs an induction technique.
23. A method for fastening two bodies one to the other comprising
the steps of: providing two opposed bodies, providing a shank
having a grip member and a clinching portion, the clinching portion
having at least one fiber therein, passing the shank through the
two bodies, providing an initial head affixed to the grip member,
providing a supplemental member, and staking the clinching portion
with the supplemental member sufficiently to create a unified
multi-part head.
24. The method of claim 23 including the additional step of placing
an adhesive filler material between the two bodies, the adhesive
being activated by the procedure used in the staking step.
25. The method of claim 23 wherein in the step of creating a
unified multi-part head an ultrasonic method is used.
26. The method of claim 23 wherein in the step of creating a
unified multi-part head an induction method is used.
27. The method of claim 23 wherein in the step of creating the
initial head occurs prior to the step of passing the shank through
the bodies and the filler.
28. A fastener comprising: a unified multi-part head, another head,
and a grip member extending therebetween.
29. The fastener of claim 28 wherein the other head is a unified
multi-part head.
30. The fastener of claim 28 further including a filler collocated
with the grip member and positioned between the unified multi-part
head and the other head.
31. The fastener of claim 30 wherein the filler does not contact
the unified multi-part head or the other head.
32. The fastener of claim 30 wherein the filler contains 100
percent solid adhesive.
33. The fastener of claim 30 wherein either the unified head or the
other head is staked in situate and the staking operation interacts
with the filler.
34. A method of making a rivet: providing a shank having an initial
head, passing the shank through a body, thereby defining on the
shank a gripping portion and a clinching portion, placing a
supplemental member having at least one fiber therein proximate the
clinching portion and the body, and staking the clinching portion
and the supplemental member creating a unified multi-part head.
35. A method of staking a clinch portion of a fastener comprising
the steps of: providing a clinch portion, providing a supplemental
member, staking the clinch portion into the supplemental member
creating a pre-head, wherein the staking includes a fixing
step.
36. The method of claim 35 wherein in the step of staking, the
fixing employs an ultrasonic method.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to fasteners and more
specifically to fasteners formed by staking, such as studs and
rivets.
BACKGROUND
[0002] Staked fasteners, such as studs and rivets, are a well-known
fastening technology. Studs are typically used to secure a body,
such as a circuit board, to a foundation. Rivets, on the other
hand, are typically used to fasten two bodies, such as sheet
materials, together at an overlapping seam. For either a stud or a
rivet, fastening is accomplished by the creation of a head on a
shank. In the case of a stud having two ends, a head is formed on
one end of the shank with the other end fixed to the foundation
with the body therebetween. In the case of a rivet, heads are
formed on both ends of the shank with the bodies therebetween.
[0003] A staked fastener can be made from many materials, such as
steel, aluminum and plastic. Where weight is a concern, such as in
an airplane, helicopter, or spacecraft, materials with high
strength-to-weight ratios, such as plastic, are preferred.
Unfortunately, plastic rivets simply do not have the ultimate
strength of rivets made from other materials. As a result, plastic
rivets, though desirable for many applications, cannot be
practicably used, or in some cases used at all.
[0004] There have been many advances in the plastic rivet. From an
initial beginning when plastic rivets were simply all plastic, such
as a thermoplastic (e.g., polyetheretherketone (more commonly known
as "PEEK")), newer composite plastic rivets have some type of
reinforcement added to the plastic. For example, many composite
plastic rivets are reinforced with fibers, such as carbon or
glass.
[0005] Rivets are typically formed in a two step process. First, an
initial head is formed with a shank extending therefrom. Generally,
the initial head is formed in a factory setting by a machine, by
molding or staking an end of a rod, which tends to make a high
quality initial head with a properly contoured contact surface (the
surface of the head that will abut the body). Also, additional
fabrication of the initial head, such as cleanup of the contact
surface, can be performed relatively easily.
[0006] Then in an application, a second head is formed in situate
on the end of the shank. More specifically, when a rivet is used in
an application, such as connecting two bodies, a hole is made in
each of the two bodies. The diameter of the holes is sized such
that when the holes are aligned with each other the shank can pass
through, but the initial head can not pass through the first hole
that the shank passed through. The second head is then formed on
the other end of the shank, thereby securing the two bodies
together.
[0007] Unlike the initial head, the second head is formed at the
job site, typically using a hand held tool, thus the conditions are
not as controlled as those during the formation of the initial
head. Additionally, cleanup of its contact surface is impossible,
as it is abutting the body. As a result, the precision of the
contact surface of the second head is generally not to the level of
that of the contact surface of the initial head. This discrepancy
results in a second head with less strength than the initial
head.
[0008] More specifically, many processes used on plastic rivets to
form the second head create voids in the contact surface of the
rivet head. As a result, the head has a local weakness at its
parameter edge. If pressure is applied thereto, it will cause a
local failure of the head. These local failures result in "play"
between the rivet and body, thereby creating the unacceptable
amount of movement between the head and the shaft, causing the
rivet to fail.
[0009] What is needed in the art is a staked fastener head and way
to make the head such that the resulting rivet, or stud, is
stronger than it otherwise would be.
SUMMARY OF THE INVENTION
[0010] This invention is a unified multi-part head and a method for
making it for a staked fastener, such as a rivet. In an exemplary
embodiment of a rivet employing the unified multi-part head, a
shank with two ends has an initial head formed at one end.
Proximate the other end is at least one fiber embedded in the
shank. In an application, the shank is passed through a body and a
unified multi-part head is formed by staking the shank's other end,
thereby trapping the body between the heads. In forming the unified
multi-part head, a first member is created from a clinch portion of
the shank (which has at least a portion of the at least one fiber
therein), and a supplemental member placed proximate the first
member such that the supplemental member is trapped during staking
between the forming first member and the body. Additional
sufficient energy is applied during staking such that at least one
of the at least one fibers will become a shared fiber (a fiber
having one segment embedded in the supplemental member and another
segment embedded in the first member).
[0011] These and other features, aspects, and advantages of
embodiments of the present invention will become apparent with
reference to the following description in conjunction with the
accompanying drawings. It is to be understood, however, that the
drawings are designed solely for the purposes of illustration and
not as a definition of the limits of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows a side view of a rivet connecting two bodies
having a unified multi-part head of the present invention.
[0013] FIG. 2 is a series of three drawings, individually
identified as A, B, and C, each taken along cross-section 2-2 of
FIG. 1, showing the creation of a unified multi-part head of the
present invention.
[0014] FIG. 3 shows a perspective view of a style of supplemental
member for use in the present invention.
[0015] FIG. 4 shows a perspective view of another style of
supplemental member for use in the present invention.
[0016] FIG. 5 is a cross-sectional view of the supplemental member
shown in FIG. 4 taken along line 5-5.
[0017] FIG. 6 is a perspective view of another style of
supplemental member for use in the present invention.
[0018] FIG. 7 is a side view of the supplemental member depicted in
FIG. 6.
[0019] FIG. 8 is a cross-sectional view of the supplemental member
depicted in FIG. 6 used in an application.
[0020] FIG. 9 is an expanded perspective view of another embodiment
of a supplemental member.
[0021] FIG. 10 is an expanded perspective view of another
embodiment of a supplemental member.
[0022] FIG. 11 is a side view of another embodiment of a
supplemental member.
[0023] FIG. 12 is a side view of the supplemental member depicted
in FIG. 11 having another orientation.
[0024] FIG. 13 is yet another style of supplemental member for use
in the present invention.
[0025] FIG. 14 is a cross-sectional side view of another shape of a
first member of the present invention.
[0026] FIG. 15 is a top view of the first member depicted in FIG.
14.
[0027] FIG. 16 is a cross-sectional view of a stud employing a
supplemental member.
DETAILED DESCRIPTION
[0028] Referring to FIG. 1, a rivet, generally referred to by
reference number 10, secures a first body 12, such as a sheet
material, to a second body 14, such as a sheet material. The rivet
10 has an initial head 16 having a contact surface 18, a unified
multi-part head (generally referred to by reference number 20)
having a contact surface 22, and a grip member 24. The unified
multi-part head 20 has a first member 26, which is formed from a
clinch portion 28, and a supplemental member (not easily seen in
this view, discussed below).
[0029] The grip member 24 and the clinch portion 28 are separate
segments of a shank 30, which extends outwardly from the initial
head 16. In the embodiment depicted in FIG. 1, the grip member 24
is that segment of the shank 30 passing through holes 32, 34, which
are defined by the first and second bodies 12, 14. The clinch
portion 28 (depicted by dotted lines) is the segment of the shank
30 extending outwardly beyond a surface 35 of the second body 14.
As those skilled in the art will appreciate, the precise
demarcation between the grip member 24 and the clinch portion 28 of
the shank 30 is a function of the style of head (flush, as shown,
or countersunk), which determines the contact surface of the head.
Thus, the demarcation point should not be strictly construed to
begin at the surface of the body from which the shank extends, as
shown in this exemplary embodiment. Additionally, the use of
additional elements, such as washers, may alter the demarcation
point. Also, it should be appreciated that the initial head 16
could be formed from another clinch portion of a rod (not shown),
thereby creating the shank 30 with the initial head 16.
[0030] Referring to the series of Figures that comprise FIG. 2, the
rivet 10 has the unified multi-part head 20 formed in the following
manner. As shown in FIG. 2A, the rivet 10 originally has the
initial head 16 and the shank 30, with the grip member 24 and the
clinch portion 28, which has an end 36. An enlarged view of the
clinch portion 28 of FIG. 2A, shows at least one fiber 38 contained
therein. The at least one fiber 38 in the clinch portion 28 is
oriented generally parallel to the centerline of the shank 30.
[0031] A supplemental member 40 is collocated with the clinch
portion 28 of the shank 30 proximate the second body 14. Further
discussion of the supplemental member 40 is presented below.
[0032] Continuing with FIGS. 2B and 2C, the first member 26 is
formed by staking the end 36 of the clinch portion 28 with a
staking tool (not shown). The staking operation continues over a
distance d.sub.s until the unified multi-part head 20 is
formed.
[0033] As shown in the expanded view of FIG. 2B, the staking
operation, which may utilize a staking tool, such as one having a
semi-hemispherical shape (not shown), tends to bend the at least
one fiber 38 in the first member 26 toward a perimeter segment 42,
which will eventually abut the supplemental member 40. A void 44
defined by the perimeter segment 42 of the first member 26 may be
formed during the staking operation.
[0034] As shown in FIGS. 2B and 2C, the staking operation brings
the first member 26 into contact with the supplemental member 40.
The energy from the staking operation enters the supplemental
member 40 causing it to deform to the contour of the perimeter
segment 42, entering the void, and forming at least part of the
contact surface 22 of the unified multi-part head 20.
[0035] The staking procedure imparts to at least one of the at
least one fibers 38 and the supplemental member 40 sufficient
energy such that a portion of those fibers cross the boundary and
become embedded in the supplemental member 40. As a result, at
least one of the at least one fibers 38 will become a shared fiber
45. The shared fiber 45 being a fiber that is simultaneously
embedded in the first member 26 and the supplemental member 40. In
other words, the shared fiber 45 will have a segment embedded in
the first member 26 and a segment embedded the in supplemental
member 40. As shown in FIG. 2C in the expanded view, a shared fiber
45a could cross the perimeter segment 42 more than once.
[0036] The staking method employed depends upon the materials
selected for the clinch portion 28 and the supplemental member 40.
For example, where the clinch portion 28 and the supplemental
member 40 are plastic, such methods as ultrasonic and/or induction
could be used.
[0037] The staking procedure to create a shared fiber 45, however,
is different than conventional procedures. In a standard ultrasonic
procedure, the staking procedure is controlled by the distance
d.sub.s the staking tool must travel to accomplish the formation of
the relevant head. More specifically, sufficient energy is applied
to the clinch portion 30 via the staking tool to cause the clinch
portion to flow thereby allowing the staking tool to act on the
clinch portion to travel the distance d.sub.s to deform the clinch
portion into a desired head shape. Once the desired head shape is
accomplished, i.e., the travel distance d.sub.s has been
accomplished, the energy is removed, but the staking tool is held
in position for some hold time. The hold time allows the head,
which is under the staking tool and still fluid enough to flow, to
cool sufficiently so that the staking tool can be removed without
the clinch portion further flowing. In the procedure of the
invention, there is fixer step in the staking procedure that occurs
after the travel distance ds has been accomplished prior to the
hold. In the fixer step, energy is still applied, generally at the
level previously used, to the pre-head (the head as it exists
immediately after the travel distance d.sub.s has been reached).
The fixer step adds additional energy to the pre-head to create the
shared fiber 45, thereby converting the pre-head to a unified
multi-part head 20. The amount of energy is application dependent
depending on such factors as the materials used in the pre-head and
their associated masses. Depending upon the degree of additional
energy added during the fixer step and the materials used, the
supplemental member 40 and the first member 26 may merely be welded
to each other or may form a coherent mass.
[0038] If induction staking is used, materials that generate heat
when exposed to induction energy would most likely have to be
present in the clinch portion 30, but could be present elsewhere,
such as in the supplemental member 40.
[0039] The supplemental member 40 can be of almost any shape, such
as a rectangular solid (FIG. 3), a washer (FIG. 4), a keyed
structure (FIG. 6), or a graduated structure (FIG. 11). Typically
these types of structures have a hole 46, 48, 50 and 71, which is
defined by the supplemental member 40, sized to allow the clinch
portion 28 of the shank 30 to pass through.
[0040] The supplemental member 40 should have a sufficient initial
volume V1, V2, V3, V4 to permit it to at least fill the void 44.
The supplemental member 40 may have a greater volume than that
necessary to fill the void 44 that will simply flow out during the
staking operation. As those skilled in the art will appreciate,
some material of the first member 16 may also flow out from under
the staking tool as it travels the distance d.sub.s, causing a
decrease in the density of the first member 16. Therefore, the
volume V1, V2, V3, V4 of the supplemental member 40 may be
sufficiently increased above that required to fill the void 44 to
compensate for this loss in density.
[0041] As depicted in FIG. 5, at least one fiber 54 could be
incorporated in the supplemental member 40. It is, therefore,
within the scope of the invention if at least one of the at least
one fibers 54 from the supplemental member 40 becomes a shared
fiber 45 regardless of whether the clinch portion 28 of the shank
30 has fibers or not.
[0042] Referring to FIGS. 6, 7, 8, 9 and 10, the supplemental
member 40 may be a keyed structure. As shown in FIGS. 6 and 7, a
supplemental member 40 has a keyed structure of a top-hat design
having a brim 56 with a crown 58 extending therefrom. In one
application, the crown 58 is inserted into the hole 34 of the
second body 14, and the shank 30 of the rivet 10 is inserted
through the hole 54 such that the clinch portion 28 extends
outwardly from the brim 56. As shown in FIG. 8, in a keyed
structure, a portion, i.e., a key, of the supplemental member 40,
such as the crown 58, can be positioned between the grip member 24
of the shank 30 and the second body 14 and even into the first body
12.
[0043] The keyed structure may also have the additional feature of
a non-rotational cross-sectional shape such that in cooperation
with the cross-sectional shape of the hole the supplemental
material will not rotate within the hole defined by the body, or
bodies. For example referring to FIGS. 9 and 10, the hole 34 and
the supplemental member 40 could have a crown 58 with a
complementary rectangular cross-sections, or a corresponding
protrusion 62 and slot 64.
[0044] The supplemental member 40 may also be graduated. Referring
to FIG. 11, an example of a graduated design for a supplemental
member 40 in the form of a top-hat having a brim 66 and a crown 68.
In application, the crown 68 would most likely extend outwardly
from the surface 35; however as shown in FIG. 10 the graduated
member could have the opposite orientation. Depending upon the
application, other graduated shapes, such as frustum of pyramid,
could be used.
[0045] The supplemental member 40 may also be designed to engage
the clinch portion. Engagement could be by friction or mechanical
fastener. As shown in FIG. 12, the fastener could be grips 70 for
engaging the clinch portion 28 extending outwardly from a surface
72 that defines the hole 71. The fastener could be of a one-way
design, i.e., the fastener is broken to effectuate removal of the
supplemental member 40.
[0046] Referring to FIG. 13, the supplemental member 40 could also
be a wrap 60, such as a cord or tape, applied around the rivet 10,
most likely the grip member 28 proximate the second body 14. The
cross-section of the wrap 60 could be any shape.
[0047] While the results of a hemispherical shaped head for a
staking tool have been previously depicted, other shapes can be
used. FIGS. 14 and 15 depict a symmetrical unified multi-part head
20. The symmetrical multi-part head 20 has a first member 26 where
the at least one fibers 38 generally extend radially from the
centerline of the clinch portion 28. This symmetry is accomplished
by using a staking tool 74 with a shank center locator 76. The
shank center locator 76 penetrates into the clinch portion 28 of
the shank 30 on the longitudinal axis causing the at least one
fibers 38 to be splayed radially outwardly therefrom.
[0048] Materials for the rivet 10 and supplemental member 40 are a
matter of design choice. Typical plastics, which include
thermoplastics, such as PEEK or polyetherimide (more commonly known
as PEI), are particularly well suited for the invention. As
discussed above, staking may cause a weld to occur between the
material of the rivet 10 and the supplemental member 40 and even
between the rivet and/or the supplemental member and the second
body 14.
[0049] As those skilled in the art will appreciate, the strength of
the weld or whether a coherent mass is formed between the first
member 26 and supplemental member 40 is, among other things,
dependent upon the materials from which the rivet and supplemental
member are made. If the rivet and supplemental member are made from
compatible or the same material, the weld could be stronger and the
coherent mass more uniform than it might otherwise be.
[0050] Any fibers can be embedded into the plastic of the rivet 10
or supplemental member 40. Fibers are also a matter of design
choice and may include carbon or glass. Carbon fibers are
particularly strong and lightweight.
[0051] The at least one fiber 38 in the shank 30 has been depicted
in FIG. 2 as being oriented generally parallel with the centerline
of the shank 30, but the at least one fibers could have any
orientation. Where there are two or more fibers 38 in the shank 30,
they could be randomly oriented one to the other. Additionally, the
at least one fibers 38 can be of any length, even running from end
to end through the grip portion and clinch portions of a rod (not
shown) from which the rivet 10 was created. Also in the case of
multiple fibers 38, fibers of varying lengths could be used.
Therefore, depending upon the length of the particular fibers in
the first member 26, a majority of the length of the shared fiber
45 could be in the first member, or in the supplemental member 40.
This is equally true for the at least one fibers 54 incorporated in
the supplemental member 40.
[0052] Referring to FIG. 2, a filler 78 maybe added about the grip
member 24 between the two bodies 12, 14. The filler 78 can be of
any shape, such as a washer, and be made from any number of
materials to meet any particular need. For example, the filler 78
could contain a rubber or neoprene to provide a seal, or an
adhesive, such as a 100% solids adhesive, that would be activated,
in the case of a 100% solids adhesive melt and flow, as a result of
the staking operation for providing additional bonding between the
first and second bodies 12, 14.
[0053] Referring to FIG. 16, in the case of a stud 80 having one
end affixed to a foundation 82, it would be beneficial to create a
stop 84 to support the filler 78. The stop 72 could be created in
any number of ways such as by a notch in or taper of the shank
30.
[0054] While there has been illustrated and described what is at
present considered to be preferred and alternative embodiments of
the claimed invention, it will be appreciated that numerous changes
and modifications are likely to occur to those skilled in the art.
For example, while the unified multi-part head has been shown for a
rivet, it is equally applicable for use with a stud. In addition,
the unified multi-part head could be used for both heads of a
rivet. Also, the use of the singular should be interpreted to mean
at least one unless the specification makes such expressly clear.
It is intended in the appended claims to cover all those changes
and modifications that fall within the spirit and scope of the
claimed invention.
* * * * *